/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.rest.handler.cluster;

import org.apache.flink.api.common.time.Time;
import org.apache.flink.runtime.rest.handler.AbstractHandler;
import org.apache.flink.runtime.rest.handler.HandlerRequest;
import org.apache.flink.runtime.rest.handler.util.HandlerUtils;
import org.apache.flink.runtime.rest.messages.EmptyRequestBody;
import org.apache.flink.runtime.rest.messages.ErrorResponseBody;
import org.apache.flink.runtime.rest.messages.MessageParameters;
import org.apache.flink.runtime.rest.messages.UntypedResponseMessageHeaders;
import org.apache.flink.runtime.webmonitor.RestfulGateway;
import org.apache.flink.runtime.webmonitor.retriever.GatewayRetriever;
import org.apache.flink.util.FlinkException;

import org.apache.flink.shaded.netty4.io.netty.channel.ChannelHandlerContext;
import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpRequest;
import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpResponseStatus;

import javax.annotation.Nullable;

import java.io.File;
import java.util.Collections;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionException;

/**
 * Base class for serving files from the JobManager.
 */
public abstract class AbstractJobManagerFileHandler<M extends MessageParameters> extends AbstractHandler<RestfulGateway, EmptyRequestBody, M> {

	protected AbstractJobManagerFileHandler(
			GatewayRetriever<? extends RestfulGateway> leaderRetriever,
			Time timeout,
			Map<String, String> responseHeaders,
			UntypedResponseMessageHeaders<EmptyRequestBody, M> messageHeaders) {
		super(leaderRetriever, timeout, responseHeaders, messageHeaders);
	}

	@Override
	protected CompletableFuture<Void> respondToRequest(ChannelHandlerContext ctx, HttpRequest httpRequest, HandlerRequest<EmptyRequestBody, M> handlerRequest, RestfulGateway gateway) {
		File file = getFile(handlerRequest);
		if (file != null && file.exists()) {
			try {
				HandlerUtils.transferFile(
					ctx,
					file,
					httpRequest);
			} catch (FlinkException e) {
				throw new CompletionException(new FlinkException("Could not transfer file to client.", e));
			}
			return CompletableFuture.completedFuture(null);
		} else {
			return HandlerUtils.sendErrorResponse(
				ctx,
				httpRequest,
				new ErrorResponseBody("This file does not exist in JobManager log dir."),
				HttpResponseStatus.NOT_FOUND,
				Collections.emptyMap());
		}
	}

	@Nullable
	protected abstract File getFile(HandlerRequest<EmptyRequestBody, M> handlerRequest);
}
